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How would you make a 120VAC powered beep/chime ?

Discussion in 'General Electronics Discussion' started by Externet, Sep 4, 2017.

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  1. Externet


    Aug 24, 2009
    For an elderly person that forgets to turn off the electric stove; I would like to add inside the control panel, a periodic beep once a minute as a reminder when a 'burner' is on.

    Without adding a low voltage power supply, tapping from the neon 'ON' indicators, when energized, something that makes a brief noise every minute would be great. How would you do it ?

    Obviously, a piezo buzzer or speaker would not handle high voltage, plus a 'timing' something would be needed...
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    This is imho the most simple and least dangerous method: Connect e.g. a USB wall wart's input in parallel to the indicator. Use the 5 V output to power a simple timer, e.g. based on a 555 and a piezo buzzer for output. The only safety relevant connection you'll have to make is from the indicator to the wall wart. Everything else is low voltage and safe.
  3. 73's de Edd

    73's de Edd

    Aug 21, 2015
    Sir Externet . . . . .

    Use this line powered circuit or hand fabricate a NE-2 to photocell optocoupler interface to trigger a separate LV powered beep circuit. . . . . . (I still like NE-2's and NE-51's for certain applications . )

    AC powered Piezo Beeper.png
    A higher C! capacitance gives more " PUNCH " to the beep.
    Increasing R1 resistance or increasing Cx capacitance spreads out the time between beeps. . . . . with a higher value of Cx giving a louder beep.

    73's de Edd

    Harald Kapp likes this.
  4. Externet


    Aug 24, 2009
    Thanks, gentlemen.
    Harald : That was my second choice to do it, by powering a USB cube adapter directly from the neon indicator in the stove panel.:)
    Edd: That is what I envisioned, but I was wondering if a diac would be implementable. Your Ne-2 would work as a relaxation oscillator until 100n depletes; right ?:)

    I will digest a combination of both to avoid a burst generator (Ne556) circuitry... Will see what contraption comes out.:rolleyes:
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